Prismatic telescope.



PATENTED DEC. 27, 1904.

H. C. MUSTIN.

PRISMATIG TELESCOPE.

APPLICATION FILED APR. 26,1904.

2 SEEETSSHEET 1,

Nb. 778.694. PATE'NTED 'DE'G.2'7'.1904.

H. 0. MUSTIN. PRISMATIG TELESCOPE.

APPLICATION FILED APB. 26,1904- 2 SHEETSSHBET 2.

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UNITED STATES Patented December 27, 1904.

HENRY C. MUSTIN, OF PHILADELPHIA, PENNSYLVANIA.

PRlSMATIC TELESCOPE.

SPECIFICATION forming part of Letters ?atent No. 778,694, dated December 27, 1904.

Application filed April 26, 1904- Serial No. 204,979.

To t w/tmn it puny concern:

Be it known that I, HENRY G. MUs'rIN, a lieutenant in the United States Navy, residing at Germantown, in the city of Philadelphia and State of Pennsylvania, haveinvented certain new and useful Improvements in Prismatic Telescopes; and I do hereby declare the following to be afull', clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to improvements in telescopes, and especially to that type wherein the optical axis is caused to be deflected so that the optical axis of the object-glass or objective opening lies in'a different plane from the optical axis of the eyepiece, whereby an object may be viewed from behind a cover without the exposure of the person using the in strument.

The principal object of the invention is to invert the image without the employment of lenses for this purpose and to reduce to a minimum the number of entry and emerging surfaces through which the rays must neces sarily pass, it being well known that each entry and emerging surface proportionately red uces the light at approximately two per cent. or more of the light remaining at each surfurce. To obviate this loss of light, it is apparent, is an especially desirable feature, particularly where the telescope is to be employed for nocturnal use.

Another object of the'invention is to so construct and arrange the combination of prisms hereinafter referred to that their disposition in the telescope-tube will be substantially in alinement longitudinally of the tube, whereby a very compact instrument is produced, the prisms being encompassed by a tube in cross-section no greater substantially than the leg-surface of the entrant-prism, while the instrument possesses at thesame time all the advantages of a telescope with an angular line of sight and erecting means independent of auxiliary erecting-lenses.

It will also be obvious that in a telescope of this character the disposition of the real image along the optical axis of the eyepiece will be varied in proportion to the distance of the object from the objective-lens. This being true, great difficulties are experienced by the fact that oftentimes the virtual or magnified image is partially obscured by the cross-hairs 0f the instrument being magnified in a proportion greater than the magnification of the real image. It is particularlydesirable, therefore. that the positions of the real image and the cross-hairs coincide in every instance so that they will be magnified with the same intensity; and it is another principal object of the present invention to accomplish this end by providing means for adjusting the cross-hairs longitudinally of the eyepiece, whereby the cross-hairs may be brought to coincide with the real image irrespective of the varying positions of the real image along the optical axis of the eyepiece.

In carrying out my invention I employ a system of prisms which differentiate from the combination of prisms of the well known Porro telescope in their particular arrangement and disposition relatively to each other. Although, like Porros combination of prisms, the optical axis is deflected four times at angles of ninety degrees each, unlike the same by my arrangement the emerging rays from the prisms are only deflected twice at angles of ninety degrees, while the prisms themselves are not arranged in combination as a unit, but are separated and suitably disposed relatively to each other at different ends of the telescope opposite the objective and the eyepiece, respectively.

To more fully describe the invention and the particular features of novelty embodied in the claims, reference is had to the accompanying drawings, illustrating the same, in which like reference letters and numerals designate the same parts in the several views, in which Figure 1 is a longitudinal transverse section through the telescope'tube, the prisms being shown in plan; Fig. 2, a longitudinal vertical section, the prisms being shown in side elevation; Fig. 3, a diagrammatic plan view, the prisms at the eyepiece end of the tube being shown disassociated for the purpose of clearer illustration; Fig. 4, a similar diagrammatic view in side elevation, and Fig. 5 a modilied disposition of the object-glass.

A is the object-glass, and B is the eyepiece, carrying a suitable arrangement of magnifying-glasses L.

C is the telescope-tube, the front and bottom sides U and C, respectively, being preferably straight surfaces, at the forward end of which is arranged the rim 0 disposed at right angles thereto for the reception of the object-glass when used in the position forward of the first prism, it being understood that the object-glass may be either located in front or to the rear of the prism. The outer end wall 0* of the tube C diverges rearwardly and inwardly at an angle of forty-five degrees from the front sides a to meet the rear side 0", which, together with the top side 0", inclines toward the opposite end of the tube. At the eyepiece end of the tube is formed a housing for the prisms located at that end, compris ing the squared walls 0 and the angular walls ,0, formed by the continuation of the top side 0 merginginto the bottom side 0, the front face being a continuation of the front side 0 and the rear face a continuation of the rear side 0, an aperture being disposed in the latter and a tube 1) formed thereon, the outer end being flanged, as at I)", for the reception of the adjustable eyepiece B.

Any suitable means may be utilized for adjusting the cross-hairs relatively to the real image; but for the purposes of illustration I will describe a specific construction for attaining this end.

E represents a short tubular section located within the tube D to the rear of the flanged end D". This tubular section E is of such diameter as to snugly fit within the tube D, but adapted to be readily moved longitudinally thereof. The cross-wires F are disposed within the short tubular section E, as clearly shown. The lower peripheral surface of the tube-section E is provided with a rack, (shown in dotted lines at (1,) and opposite this rack and disposed in the same direction is cut a slot (Z in the lower peripheral surface of the tube D. An adjustment-spindle g is suitably suspended by depending lugs, (not shown,) and one end of the spindle is provided with a milled head G and the other head with a pinion adapted to register with the slot (Z and engage the teeth on the rack a. By this arrangement-it will be readily seen that the cross-hairs may be delicately adjusted along the optical axis of the eyepiece independently of the adjustment of the eyepiece, and vice versa.

1 is a right-angled isosceles prism, the hypotenuse 1 resting snugly against the outer wall 0" and the leg-surfaces 1 and 1, respectively facing the objective and the longitudinal bore of the tube C. 2 is a right-angled isosceles prism formed by two right-ai'igled isosceles prisms joined at their bases in such a manner that their hypotenuse sides 2 and 2" diverge at a right angle to each other and are adapted to rest snugly against the angular walls 0, the hypotenuse-surface 2 of the two prisms taken conjointly being disposed parallel to the surface 1 of the prism 1 and at right angles to the surface l of the latter prism and the lower face of the hypotenusesurface 2 being opposed to and in line of the rays emerging from the surface 1. 3 is a right-angle isosceles prism located in the housing 0 the hypotenuse-surface 3 being disposed toward the front side 0 of the tube. with one leg 3 opposite the eyepiece B. The other leg-surface, 3, of this prism is suitably cemented, as with Canada balsam, to the upper face of the hypotenuse 2 of the double prism, or it maybe formed integral therewith. this particular arrangement of the prisms it will be seen that the image is turned around twice through an angle of ninety degrees, whereby it is erected at the eyepiece without the interposition of an erecting-lens. At the same time a tube of comparatively small crosssection may be used, as the leg-surface 1 of the entrant-prism is of an area suflicicnt to substantially oppose the lower hypotenuse-surface 2 of the prism 2 and the hypotenuse surface 3 of the prism 3, whereby the whole set of prisms are arranged in substantial alinement longitudinally of the tube. In Fig. 5 l have illustrated an arrangement whereby a further saving of light is attained by dispensing with the entry=surface of the first prism with respect to the object-glass. In this construction the object-glass is split sub= stantiallly on the line 5 of Fig. 3, the outer section A being suitably cemented to the surface 1 of the prism and the inner section A to the surface 1.

Referring now to Figs. 3 and 4t, the object X is upset and inverted upon passing through the object-glass, as at X. The rays entering the prism 1 are totally reflected at the points :1: on the hypotenuse 1 and emerge from the surface 1 (the first emergent-surface) at an angle of ninety degrees, the image X being still upset, but disposed at an angle perpendicular to its disposition at X". The rays now pass along the lines Y Z below the prism 3 and enter the lower face of the hypotenusesurface 2" of double prism 2, are totally reflected at a" 1/ on the hypotenuse-surface 2 along the lines Y Z to the points a! g/ on the hypotenuse-surface 2, are again totally refiected at these points along the lines Y Z (the image being righted, as at X", but still disposed in the same direction as at X,) thence strike the hypotenuse-surfaee 3 of the prism 3 at the points in" are again totallyreflected along the lines Y Z" and emerge from the surface 3 (the second emergent-surface) at angles of ninety degrees, the inverted real image appearing as at X in proper relative disposition to the object X. As heretofore mentioned, the real image X appearing in the tube will be disposed at a point along the optical axis of the eyepiece determined by the distance of the object from the objective. By operating the eyepiece to bring the real image X into proper focal distance the virtual image will appear magnified, and the cross-hairs should now be adjusted until they coincide with the real image, .as will be evidenced by the lines being brought out sharply in the virtual resultant. It will be observed that at the eyepiece end of the telescope there were three total internal reflections of the rays from the time of entry to emergence two total reflections within the double-prism 2 and one total reflection in the prism 3.

It is to be understood that although I have described the arrangement of prisms as particularly applicable to a telescope that by combining and suitably arranging two of the telescopes the invention may be readily applied to a binocular-glass for marine or field purposes. It is also obvious that although I have described the optical axis of the objective and the eyepiece as being substantially at right angles to the tube C they may readily be disposed at other angles thereto by a corresponding slight rearrangement of the prisms.

Other modifications might be made without departing from the spirit of my inven-- tion; but

IVhat I claim is- 1. In a telescope, the combination with a tube provided at opposite ends with a laterally-disposed objective and a laterally-disposed eye-lens, of a total-reflecting prism having one leg-surface disposed opposite said objective and the other leg-surface disposed transversely of said tube, a twice-totally-refleeting prism adjacent said eye-lens and having substantially one half of its hypotenusesurface opposed to the transverse leg-surface of said first prism, and athird total-reflecting prism having one of its leg-surfaces joined to the remaining half of the hypotenuse-surface of said twice-totallyreflecting prism, and said third prism having its other leg-surface opposed to said eye-lens.

2. In a telescope the combination with a tube provided at opposite ends with a later-- and having its other leg-surface opposed to but one entry and one emerging surface and.

so disposed relatively to said first prism and eye-lens as to receive the rays from said first prism and deflect the same to said eyelens.

4:. In a telescope comprising a tube provided with an objective and an eye-lens, and means for erecting the real image, in combination with cross-hairs and means for adjusting said cross-hairs, relatively to the real image, along the telescopes optical axis.

5. In a telescope comprising a tube provided with an objective and an eye-lens, and means for erecting the real image, in combination with cross-hairs and means for ad justing said crosshairs relatively to the real im' age, comprising a slide carrying the crosshairs within said tube adjacent said eye-lens,

and means for operating said slide along the v telescopes optical axis.

6. In a telescope having-an angular line of sight,the combination with the telescope-tube provided with objective and eye openings, of an eye-tube opposite said eye-opening, means for erecting and deflecting the image to said eye-tube, cross-hairs located within said eyetube, and means for adjusting said cross-hairs along the optical axis of said eye-tube with respect to the real image formed.

7. In a telescope having an angular line of sight, the combination with a tube proper provided with an opening located substantially at opposite ends of said tube and disposed angularly thereto,- of an eye-tube adja cent said eye-opening, means for erecting the image and deflecting the same to said eyetube, movable cross-hairs mounted in said eye-tube, means for adjusting said cross-hairs along the optical axis of said eye-tube relatively to the real image, and an eyepiece provided with a magnifying-lens operatively associated with said eye-tube.

8. In a telescope having an angular line of sight, the combination with the tube proper provided with an objective and an eye opening angularly disposed at opposite ends thereof, of an eye-tube adjacent said eye-opening, means for erecting the image and reflecting the same to said eye-tube, a movable cylindrical support within said eye-tube, crosshairs mounted within said cylindrical support,

IIO

means for adjusting said cylindrical support along the optical axis of said tube comprising an adjusting-screw operatively connected to said cylindrical support, and an eyepiece adjustable along said eye-tube.

9. In a telescope having an angular line of sight, the combination with the tube proper provided with an objective and an eye opening angularly disposed thereof and arranged out of alinement with each other, of an eyetube adjacent said eye-opening, means for deflecting and erecting the image comprising a total-reflecting prism opposite said objectiveopening and a combination of prisms so arranged adjacent said eye-opening as to receive the rays from said first prism and refleet the same to the eye-tube in three total internal reflections, of cross-hairs adjustably supported within said eye-tube, and means for operating said cross-hairs along the optical axis of said eyepiece relatively to the erected real image.

10. In a telescope the combination with a tube provided with an objective and an eyelens, of means interposed between same for deflecting and. erecting the image, comprising a prism disposed adjacent the objective and a plurality of combined prisms separated from said first prism, said combined prisms being so arranged relatively to said first prism and eye-lens as to receive the rays from said first prism and deflect the same to said eye-lens, cross-hairs, and means for adjusting said crosshairs, with respect to the real image formed along the teleseopes optical axis.

11. In a telescope the combination with a tube provided with an objective and an eyelens arranged outofalinement, of means interposed between same for deflecting and erecting the image, comprising atotal-reflecting prism located adjacent said objective for deflecting the rays toward said eye-lens at right angles thereto, and a plurality of combined prisms adjacent said. eye-lens, said combined prisms being so disposed relatively to each other and to said first prism and eye-lens as to receive the rays from said first prism, totally reflect the same in three and only three internal reflections and deflect same to said eye-lens, crosshairs, and means for adjusting said crosshairs, with respect to the real image formed, along the telescopes optical axis.

12. In a telescope the combination with a tube provided with an objective and an eye lens arranged out of alinement, of a total-refleeting prism having one leg-surface disposed opposite said objective and the other leg-surface disposed transversely of said tube, a twice-totally reflecting prism adjacent said eye-lens and having its lower hypotenuse-surface opposed to the transverse leg-surface of said first prism, a third total-reflecting prism cemented on one leg-surface to the upper hypotenuse-surface of said tWice-totally-reflecting prism and having its other leg-surface opposed to said eye-lens, cross-hairs, and means for adjusting said cross-hairs, with respect to the real image formed, along the telescopes optical axis.

13. In a telescope the combination with a tube provided with an objective and an eyepiece, said tube being of such dimensions in cross-section as to receive a suitable combination of opposed prisms arranged substantially in longitudinal alinement, of prisms, for deflecting and erecting the image, disposed adjacent the objective and eyepiece and constructed and arranged to turn the image twice through an angle of ninety degrees in planes at right angles to each other; cross-hairs, and means for adjusting said cross-hairs, with respect to the real image formed, along the telescopes optical axis.

14. In a telescope the combination with a tube provided with an objective and an eyepiece, said tube being of such dimensions in cross-section as to receive a suitable combination of opposed prisms arranged substantially in longitudinal alinement, of means interposed between said objective and eyepiece for deflecting and erecting theimage by turning the same twice through an angle of ninety degrees in planes at right angles to each other, comprising a prism disposed adjacent the objective and a plurality of combined prisms separated from said first prism and located adjacent said eyepiece; cross-hairs, andmeans for adjust ing said cross-hairs, with respect to the real image formed, along the telescopcs optical axis.

In testimony whereof I my signature in presence of two witnesses.

HENRY (J. MUSTIN.

I/Vitnesses:

A. M. HYER, OSCAR E. MAURA. 

